Process of adding bituminous additives to a fibrous material in the grinding zone of a refiner



S p 3 1968 H. K. NIELSEN, JR.. ETAL 3,

PROCESS OF ADDING BITUMINOUS ADDITIVES TO A FIBROUS MATERIAL IN THEGRINDING ZONE OF A REFINER Filed June 1, L964 2 Sheets-Sheet 1 ASPHALTIO WooD v 3. Q6 REFINER 14 Ken NER CHEST REGULATOR ,/2Z FDRRTIONERMACHINE CHEST 2 Sheets-Sheet 2 Ms e y mfiww m mw w a m wwi v VKE C 4 5 Spt 3. 1968 H. K. NIELSEN. JR.. ETAL PROCESS OF ADDING BITUMINOUSADDITIVES TO A FIBROUS MATERIAL IN THE GRINDING ZONE OF A REFINER FiledJune 1, 1964 Z 4 ilii,

United States Patent PROCESS OF ADDING BITUMINOUS ADDITIVES TO A FIBROUSMATERIAL IN THE GRINDING ZONE OF A REFINER Hans K. Nielsen, Jr.,Dunellen, David E. Noyes, Somerville, Gilbert Godin, Millington, andFred C. Norgard, Somerville, N.J., assignors to Johns-ManvilleCorporation, New York, N.Y., a corporation of New York Filed June 1,1964, Ser. No. 371,678 8 Claims. (Cl. 162171) ABSTRACT OF THE DISCLOSUREA fibrous aqueous mixture is introduced to the grinding zone of arefiner, and fluid bituminous material, e.g., asphalt, having a meltingpoint higher than the temperature of the mixture, is introduced into themixture in the grinding zone and cooled and solidified and intimatelymixed with the mixture, without clogging of the refiner.

This invention relates to the manufacture of lignocellulosic fiber andto products containing such fiber. More particularly, the inventionrelates to a process for introducing molten additives to fibrousmaterial as it is being ground an refined in preparation for manufactureof fibrous products- In the manufacture of fiber board, it has long beencommon practice to incorporate additives with the fibrous material inorder to impart certain desired properties to the final product. In manycases, this does not cause any processing difficulties, as various typesof additives may be introduced directly into the fiber refiningapparatus, or may be added to the pulp after the refining operation andprior to the felting operation. Some products, however, require theaddition of normally solid, thermoplastic substances for waterproofing,strengthening, or other purposes. Addition of these materials, such as,for example, asphalt or other bituminous substances, has been thesubject of a great deal of development work over the years, which hasresulted in several generally accepted methods of material introduction.

One method of incorporating bituminous material in fibrous stock is tointroduce it in the form of dry particles to the refining apparatus, orto mix it with the fibrous slurry after the pulp has been formed. Whilea satisfactory board product can be made from such slurries, poorretention and nonuniform distribution of the bitumen often occur.Grinding of the bitumen is often required, increasing the cost of theprocess- The type of bitumen utilized must have a relatively lowpenetration value, to permit storage without coalescence of theparticles, while at the same time possessing a low enough softeningpoint so that the material melts in the drier. Such material can beobtained from only a limited number of sources and is relativelyexpensive.

Bituminous material is also introduced to pulp slurries in the form ofan emulsion, which requires use of emulsifying agents in addition to acolloiding operation. Storage of the bituminous material is a problemwith this system, as in the dry particle method mentioned in theprevious paragraph. Boards containing bitumen introduced in this mannerare subject to problems of intermittent bitumen coverage and poorretention. In addition, the amount of emulsion which can be used islimited because it slows the drainage time of the fibrous stock aconsiderable amount.

It has been suggested to introduce bituminous material in its moltenform, either to the fibrous slurry after it has been formed and justprior to its introduction to a board forming machine, or to the beatingor mixing apparatus along with the fibrous material and water.Introduction of 3,400,043 Patented Sept. 3, 1968 molten bitumen to anaqueous slurry of fibers is described in U.S. Patent No. 3,087,851. Butthis arrangement requires special apparatus for introducing the moltenasphalt to the slurry, and furthermore, an additional refining operationis provided prior to sending the stock to the board forming machine.

Fluid bitumens have been introduced directly to a beater or mixer at thesame time that fibers and water are introduced, as disclosed in US.Patents Nos. 1,449,221, 1,844,951, and 1,878,300. According to theprocesses described in these patents, however, the fluid bitumen ismixed with hot water and cellulosic material, and the mixture ismaintained at a temperature in the mixer such that the bituminousmaterial remains in its fluid or nonsolid state. The fibrous materialremoved from the mixing apparatus is coated with the bitumen, and may befelted or molded into a product in the usual manner. This operationtakes a relatively long time, however, due to the necessity ofthoroughly mixing the materials to ensure coated fibersv In addition, itdoes not lend itself to providing a fibrous slurry containing small,discrete bitumen particles intermixed with the fibers. This type ofstock is preferred in fiberboard manufacture because the drainage timeis faster than that of stock containing bitumen coated fibers. Thebitumen in such stock becomes thoroughly mixed with the fibers in thefinal product, since at the end of the felting operation, the wetfibrous mat is dried at temperatures which melt the bitumen particles,permitting the fluid bitumen to flow and homogeneously pervade thefibrous material.

US. Patent No. 2,402,160 describes the process of introducing moltenasphalt directly into a refining apparatus specifically described as anAsplund defibrator. This type of refiner includes a steam chest intowhich slightly moist wood chips are introduced. The lignin in the woodchips, binding the fibers together, is plasticized to such an extentthat the fibers are readily sheared apart with a minimum of cutting.Liquid asphalt is forced into the preheater of the apparatus where itmixes with the wood being fed to the grinding discs, and the grindingaction in the grinding zone is carried out while the asphalt ismaintained as a liquid, resulting in asphalt coated fibers beingdischarged from the machine.

The manner of introducing asphalt in the Asplund defibrator cannot beextended to refiners such as the Bauer, Sprout-Waldron, orAllis-Chalmers mills or refiners, since such apparatus does not operatein the same manner as the Asplund defibrator. The Bauer refiner, andother apparatus of the same general type, is comprised generally of tworibbed discs rotating in opposite directions, or one rotatable discworking against a stationary plate or disc, to which discs treated woodchips, pulp, or raw wood, in the presence of a substantial amount ofwater, are fed. The material is subjected to a rubbing and partialcutting action as it passes between the ribbed surfaces of the discstoward the peripheries thereof under centrifugal forces produced by therapid rotation. Since the water introduced to the Bauer is much coolerthan molten asphalt or other molten bitumens, introduction of moltenasphalt to the mixture of wood and water would cause the asphalt toagglomerate upon contact with the water, before the mixture wassubjected to the grinding and refining action of the discs. This wouldcause an almost immediate clogging of the system. It is recognized thatPatent No. 2,402,160 discloses that the coated fiber discharged from theAsplund defibrator may be mixed with water and further refined in aBauer refiner, but this is possible because the asphalt will alreadyhave been thoroughly mixed with the wood fiber and is present only as arelatively thin coating on the fibers. Moreover, the asphalt is combinedwith only a small amount of water prior to being introduced into theBauer refiner.

Notwithstanding the years of efforts of the fiberboard industry to finda way to introduce bituminous materials efliciently and inexpensivelyinto a fibrous slurry, and to obtain a high quality, uniform product,there has been no method known to the present inventors for introducingmolten asphalt directly to the grinding zone of a refiner and obtaininga fibrous slurry containing uniformly distributed asphalt particles.

It is an object of the present invention to provide a novel process forintroducing molten asphalt, or other normally solid, thermoplasticmaterial, to a refiner without heating the grinding chamber, or thefibrous mixture fed thereto, to maintain the asphalt in a fluid state.

It is another object of the invention to provide a process forintroducing molten asphalt, or other normally solid, thermoplasticmaterial, to a refiner without having to mix the asphalt with fibrousmaterial and water prior to such introduction.

Another object of the invention is to provide a process for introducingmolten asphalt, or other normally solid, thermoplastic material, to arefiner which requires only a slight modification of existing refinerstructures.

Briefly, the invention comprises introducing an aqueous mixturecontaining fibrous material to the grinding zone of a refiner apparatus,the zone comprising grinding surfaces, one rotating with respect toanother, and introducing fluid thermoplastic material directly to thegrinding zone where, surprisingly, it does not agglomerate and clog theapparatus but is thoroughly intermingled with the aqueous mixture. Themelting point of the thermoplastic material is higher than thetemperature of the aqueous mixture, whereby the thermoplastic materialcools and solidifies upon contact with the aqueous material. By grindingthe fibrous material and the solidified thermoplastic material together,the materials are intimately mixed.

The nature of the invention will be more fully understood and otherobjects may become apparent when the following detailed description isconsidered in connection with the accompanying drawing, wherein:

FIG. 1 is a simplified flow diagram of a refining operation;

FIG. 2 is a pictorial representation of a rotary disc refiner;

FIG. 3 is a sectional view taken on the longitudinal axis of thegrinding chamber of the rotary disc refiner of FIG. 2;

FIG. 4 is a front elevational view of the grinding face of an opengrinding head or disc; and

FIG. 5 is a partial sectional view taken on the longitudinal axis ofspaced grinding discs, and showing a modified means for introducingthermoplastic material to the grinding zone.

Referring to the drawings, a typical flow diagram of a fiberboardmanufacturing process is illustrated in FIG. 1. Wood chips are stored ina bin or silo and are introduced with a predetermined amount of water toa primary refiner 12, such as, for example, a Bauer refiner. The wood isdefiberized in the refiner and the resulting pulp is delivered to arefiner chest 14, from which it is then fed to a regulator 20, wherepulp of the proper consistency is permitted to pass through aproportioner 22 and then to a machine chest 24. The pulp or slurry inthe machine chest may be introduced to a board forming machine, such asa Fourdrinier machine, where it is formed into a wet mat of fibers andsubsequently dried to form a fiberboard product.

The process steps described thus far are well known in the art. Theprocess made possible by the present invention contemplates theadditional step of adding a molten thermoplastic material, such asasphalt, to the wood chips and water in the refiner. This requires asource of molten asphalt 26, which is generally more available andinexpensive than the type of asphalt employed when mixed in its drystate. Use of molten asphalt eliminates the need for igranulating andmilling dry asphalt, and also eliminates the storage problems associatedwith the use of dry asphalt.

As previously explained, one refining apparatus to which this inventionis applicable is that which incorporates grinding discs, such as in aBauer refiner. In FIG. 2, a typical Bauer refiner 30 is illustrated ashaving a base support 32 on which are mounted two spaced motors 34 and36. Shafts 38 and 40, connected to motors 34 and 36, respectively,rotate in opposite directions and extend into a disc housing or casing42 mounted between the motors. A wood delivery chute 44 communicatingwith a source of wood chips (not shown) is connected to the upperportion of the casing 42 to permit fibrous material and water to beintroduced into the grinding zone, as will be explained in more detailhereinafter.

Referring now to FIGS. 3 and 4, the end of shaft 38 carries an open heador disc 50, and the end of shaft 40 carries a closed head or disc 52.The central portions of the discs are frusto-conical in shape, withtheir convex sides or faces directed away from the delivery chute 44,and are spaced from each other, thereby defining a grinding zone orchamber 54 therebetween. The discs have opposed peripheral portions 56and 58 to which cutting and grinding rings 60 and 62 are attached, as bybolts 64. Each ring is provided with ribs or blades 66 for grinding woodchips fed to the refiner.

As best shown in FIG. 4, the frusto-conical portion of open head '50 isprovided with three equispaced apertures 68 in order to admit wood andwater into the grinding zone between the discs. As shown in FIG. 3, aflanged ring 70 having apertures therein corresponding to the apertures68 is attached to the concave side of the open head 50 and is soarranged that the annular flange 72 thereof extends adjacent the upperportion of the delivery chute outlet 74, defining with plate 75 an inletchamber 76. Above the flange 72 and With the inlet chamber 76, a hollowplug wiper 79 is disposed so that its extremity is adjacent the openhead 50. The conduit 81 in the plug wiper 79 normally is connected to asource of water.

The operation of the standard equipment thus far described is asfollows. Wood chips are metered into the chute 44 by a metering wheel78, and water is sprayed from tubes 80 to mix with the falling chips.The mixture of chips and water moves into the inlet chamber 76, throughthe openings or apertures 68 in the open head 50, and into the grindingzone 54. Most of the mixture will pass through the openings 68 disposedadjacent the upper half of the inlet chamber, but chips and waterfalling below the shaft 38 are directed by the sloped flange 72 towardan opening 68 adjacent the lower half of the inlet chamber, throughwhich it can pass into the grinding zone 54. The mixture is hurledtoward the grinding rings 60 and 62 by the centrifugal force of therotating discs, and then passes between the ribbed rings. The wood chipsare finely ground and pulped during passage through the rotating rings,and the resulting fibrous slurry drops through an opening at the bottomof the housing 42 directly to the refiner chest or to an intermediatestorage vessel from which it is pumped to the chest. Should any buildupof fiber occur on the open head 50, it will be wiped therefrom by theplug wiper 79 which, as previously stated, is mounted closely adjacentto the head 50. Further cleaning of the head and the apertures 68 isobtained by spraying water through the conduit 81. Although not shown,additional water may be introduced to the grinding zone by sprays fromwithin the housing 42.

It has been found that molten thermoplastic material can be successfullyintroduced directly into the refiner if it is cooled and maintained innonmolten condition in the grinding zone. This may be accomplished byspraying the molten material substantially directly into the grindingzone, so that little, if any, molten material is mixed with the mixtureof water and wood chips before entering the grinding zone. When moltenasphalt, for example, is introduced into the grinding zone in thismanner, it experiences a thermal shock; that is, there is an immediateheat transfer as the material contacts the water. Drops of the asphaltspray solidify upon suddenly cooling and tend to crack or fracture intosmaller solid particles. In addition, such particles are subjected tomechanical attrition as they pass between the grinding discs. In thismanner, the molten asphalt is converted to small particles of solidasphalt in the grinding zone of the refiner, and the small asphaltparticles are intimately mixed with the wood fibers. If the moltenasphalt were introduced to the mixture of wood chips and water in thefeed chute 44, it would tend to agglomerate and clog the apparatus. Itcan be introudced in the inlet chamber 76 at a location spaced from theopen disc 50, however, so long as the velocity of the asphalt dropletsis enough to carry them into the grinding zone before they soldify or,if solidification begins before the droplets are entirely within thegrinding zone, so long as the velocity of the droplets is enough tocarry them into the grinding zone without agglomerating in the inletchamber of the apparatus.

A practical means of carrying out the method of this invention is toconnect the conduit 81 of the plug wiper 79 to a source of moltenasphalt, or to provide another molten asphalt nozzle such as indicatedat 82 in FIG. 3. By locating the asphalt spray nozzle close to the opendisc 50, substantially all of the molten asphalt first contacts themixture of water and cellulosic material in the grinding zone 54, orjust prior to entering the zone, and does not agglomerate in the inletchamber. The small amount of asphalt that accumulates on the landportions between the openings 68 in the open disc 50 is scrapedtherefrom by the wiper 79, and this material, upon being thrown intocontact with the incoming mixture of water and chips by the rotation ofthe open disc 50, is carried by the mixture into the grinding zone whereit is refined into small particles.

Several variables relating to the specific materials utilized and to theoperating requirements of the equipment must be considered. In order tointroduce asphalt in its fluid state to the refiner, it must be heatedto a temperature which exceeds its melting point by an amount sufficientto cause it to be fluidized. Also, the viscosity of the asphalt must besuch as to permit it to be pumped. In order to maintain the requiredtemperature and viscosity of the asphalt, it is desirable to pump it tothe refiner through a heated pipe.

The temperature of the mixture of chips and water introduced to therefiner preferably is ambient, but it may vary considerably according tothe temperature and type of asphalt. In order to effect a heat transfersuflicient to suddenly cool and solidify the asphalt, the mixture shouldbe cooler than the melting point of the asphalt and be present insufficient amount to effect such transfer. In order to ensure properflow, the asphalt is preferably heated to a temperature well above itsmelting point and, because it is exposed to the fibrous slurry mixturefor only a relatively short time, in the order of 1 to 2 sec- Onds, thetemperature of the mixture is preferred to be substantially lower thanthat of the asphalt.

As stated previously, it is preferred that the outlet of the nozzlespray be closely spaced from the rotating open head, as, for example,about A inch away. The asphalt should be sprayed at sufficient velocityto preclude asphalt droplets from falling to the bottom of the inletchamber and agglomerating there. The nozzle outlet may be moved closeror farther away from the head, so long as the combination of the sprayvelocity and distance from the grinding zone are such as to prevent theasphalt from solidifying and agglomeratin-g in the inlet chamber.

It is to be understood that there are methods of introducing asphalt tothe grinding zone other than by spacing a nozzle from an open grindinghead. Referring to FIG. 5, discs 50 and 52 are mounted on shafts 84 and40, respectively, as in the arrangement of FIG. 3. Instead of a separateasphalt spray nozzle, however, a conduit 86 is provided in the shaft 84,the conduit terminating at 88 in the grinding zone between the twodiscs. Thus, with this arrangement, molten. asphalt can be introduced tothe grinding zone through the conduit 86, thus eliminating the chance ofasphalt agglomeration outside of the grinding zone.

The following examples illustrate various combinations of asphalt andwater fed to a Bauer refiner under different conditions, all resultingin an intimate mixture of asphalt particles and wet fibers. In thephysical arrangement for the introduction of asphalt in the examplesgiven, a nozzle was located in the inlet chamber, and was spaced aboutinch from the open head or disc.

E xample I In practice, the type of asphalt or other thermoplasticmaterial utilized depends upon the end use of the fibrous product andthe temperature of the ovens used to dry the felted or molded product.Where the fibrous mixture is to be felted on a board-making machine, theasphalt added to the mixture generally has a softening point in therange of about 150 F. to 300 F. Asphalt has been added in amounts ashigh as of the stock mixture, based on the total dry weight of solidsand asphalt. The 80% amount is by no means the maximum amount of asphaltwhich can be added, however, since at that level, there was noindication that a peak was being reached.

As mentioned previously, this invention is not limited to the specificdisc refiner discussed, but may be practiced on modified arrangements,such as refiners employing a single rotating disc in combination with afixed plate or disc. It is not necessary that the invention be limitedto a disc type of refiner, since it could well be practiced on a plugtype refiner, for example. Basic equipment requirements are a means forintroducing molten asphalt directly into the grinding zone of a refiner,and solidifying and grinding the asphalt in the grinding zone.

While the invention has been described particularly with respect to theaddition of asphalt to a fibrous mixture, it should be understood thatany suitable thermoplastic material whose melting point is higher thanthe temperature of the water and chips introduced to the refiner can beused.

It is to be understood that variations and modifications of the presentinvention may be made without departing from the spirit of theinvention. It also is to be understood that the scope of the inventionis not to be interpreted as limited to the specific embodimentsdisclosed herein, but only in accordance with the appended claims, whenread in the light of the foregoing disclosure.

What we claim is:

1. A process for producing fibrous material intimately mixed with abituminous material, comprising the steps of:

(a) introducing an aqueous mixture containing fibrous material to thegrinding zone of a refiner apparatus, the zone comprising grindingsurfaces, one rotating with respect to another,

(b) introducing molten fluid bituminous material into the grinding zone,

the temperature of the aqueous mixture is wherein lower than the meltingpoint of the bituminous material and thereby causing the bituminousmaterial to solidify in the grinding zone.

(c) maintaining the bituminous material in solid condition in thegrinding zone, and

(cl) grinding the fibrous material and the solidified bituminousmaterial together to intimately mix the same.

2. A process for producing fibrous material is recited in claim 1,wherein the bituminous material is asphalt.

3. A process for producing fibrous material as recited in claim 2,wherein substantially all the asphalt is in molten condition as itenters the grinding zone.

4. In the process of refining fibrous material in a refining apparatuscomprising a grinding zone and a connecting material inlet chamber, thegrinding zone comprising relatively rotating grinding surfaces moving athigh speeds, the improvement comprising the steps of:

(a) introducing an aqueous mixture of relatively large pieces of fibrousmaterial to the inlet chamber,

(b) moving the aqueous mixture into the grinding zone,

(c) introducing molten fiuid bituminous material substantially directlyto the grinding zone,

wherein the temperature of the aqueous mixture is substantially coolerthan the temperature of the bituminous material and the melting pointthereof,

(d) mixing the aqueous mixture and the bituminous material in thegrinding zone a sufficient length of time to solidify the bituminousmaterial, and

(e) grinding the fibrous material and the solidified lituminous materialbetween the grinding surfaces to intimately mix the two materials.

5. A process of refining fibrous material as recited in claim 4, whereinthe bituminous material is asphalt having a melting point in the rangeof about 150 F. to about 300 F.

6. A process of refining fibrous material, comprising the steps of:

(a) introducing an aqueous mixture of fibrous material to a grindingzone comprising relatively rotating grinder surfaces in a housing,

(b) introducing molten fluid bituminous material to the grinding zone inspray form,

wherein the temperature of the aqueous mixture is substantially lessthan the melting point of the bituminous material, whereby the dropletsof the spray of bituminous material cool and solidify upon contact withthe aqueous mixture,

O (c) grinding the fibrous material and the solidified bituminousmaterial between the relatively rotating grinding surfaces in thehousing, (d) and discharging the ground and mixed fibrous material andbituminous material from the housing.

7. In a process of refining fibrous material in a refining apparatushaving:

(a) oppositely facing grinding discs spaced apart at their centralportions and in grinding relationship at their outer portions,

(b) the space between the grinding discs comprising a grinding chamber,and

(c) an inlet chamber communicating with the grinding chamber,

the steps of:

(d) introducing an aqueous mixture of cellulosic material to the inletchamber,

(e) moving the mixture into the grinding chamber,

(f) introducing molten fluid bituminous material into the grindingchamber substantially without contact with the aqueous mixture in theinlet chamber,

wherein the temperature of the aqueous mixture is considerably lowerthan the melting point of the bituminous material,

(g) mixing the aqueous mixture with the bituminous material for arelatively short period of time, but long enough to cause the bituminousmaterial to cool and solidify, and

(h) moving the aqueous mixture and the solidified bituminous materialoutwardly from the grinding chamber between the grinding surfaces of thediscs, whereby the cellulosic material and the solidified bituminousmaterial are ground and intimately mixed together and discharged fromthe grinding chamber.

8. A process of refining fibrous material as recited in claim 7, whereinthe bituminous material is sprayed into the grinding chamber.

References Cited UNITED STATES PATENTS 2,402,160 6/1946 Heritage 162103,087,851 4/1963 Beuscher et a1. 162-171 S. LEON BASHORE, PrimaryExaminer. R. BAJEFSKY, Assistant Examiner.

